ArcGIS Explorer - Control Layer Appearance

Control Layer Appearance

You can apply effects to the map to control the appearance of layers. Select the layer in the Contents window and you'll see that the Tools tab has the following functionality available in its Effects group to change the appearance of layers:

Transparency

Transparency can be used for any symbolization type, but it is especially useful for drawing raster layers with other layers on your map. This allows you to see the raster layer while still viewing underlying layers.

To adjust the transparency of a layer

1. In the Contents window, select the layer whose transparency you want to adjust.
2. Click the Transparency button on the Tools tab.
A slider bar appears which you can move to adjust the transparency of the layer and, depending on how you've set the Layers options, layers above it.
3. Move the slider bar to adjust the transparency; as you move the slider handle upward, the layer becomes more transparent.

Swipe

Use Swipe to reveal layers beneath the layer you chose to swipe and, depending on how you've set the Layers options, the layers above it. This button makes it easy to quickly see what is underneath a particular layer without having to turn it off in the Contents window or reorder layers.

To reveal layers beneath the layer you've selected

Choose the layer or group layer you want to swipe from the Contents window, then move the cursor over the map. You'll notice that the cursor changes based on whether you are resting the mouse pointer on the top, bottom, left, or right of the map. This lets you choose the direction in which you want to swipe the layer. Hold down the left mouse button and drag in the direction indicated by the mouse pointer.

Enhance

Use Enhance to adjust the brightness, contrast and gamma of raster layers and image services.

To enhance an image

1. In the Contents window, select the raster or image service layer whose display you want to enhance.
2. Click the Enahnce button on the Tools tab.
Slider bars appear which can be used to adjust the brightness, contrast and gamma of the image.
3. Move the slider bars and see the image display update to reflect the changes. In 3D the display updates when you release the slider. Pushing the button will reset the slider to the default setting for the image.

Enhance image allows you to interactively adjust the brightness (), contrast (), or gamma () of a raster layer or make the raster layer display transparently. These enhancements are applied to the rendered screen display, not to the original raster dataset values. Brightness increases the overall lightness of the image—for example, making dark colors lighter and light colors whiter—while contrast adjusts the difference between the darkest and lightest colors. Below is an example of adjustments made to the brightness and contrast of an image.

You can also apply a gamma () stretch to your image display. When preparing raster data for computer display, the gamma refers to the degree of contrast between the midlevel gray values of a raster dataset. Gamma does not affect the black or white values in a raster dataset, only the middle values. By applying a gamma correction, you can control the overall brightness of a raster dataset. If the gamma coefficient is set too low, middle tones appear too dark; however, if the gamma coefficient is set too high, middle tones appear too light, and the raster dataset looks bleached out. Gamma changes not only the brightness but also the ratios of red to green to blue.

Tips

With Swipe selected, holding down the Shift key and clicking the mouse will flicker the selected layer on and off manually. The selected layer is off as long as you hold down the mouse. Flicker is particularly useful for temporal change detection (especially of satellite images or air photographs taken at different times of the same location), data quality comparison, and other analysis where you want to see the difference between layers. Fast rates of flicker can be used to make differences between layers appear to jump out due to the optical effect of the eye being attracted to changes between rapidly alternating displays (an effect also exploited by the early experiments in cinematography).

If you hold down the Ctrl key while swiping, you'll remain in Swipe mode. This is useful if you want to continue swiping, but in a different direction, for example up/down after swiping left/right.

Holding down both Ctrl and Shift at the same time while using swipe, will allow you to flicker the display continuously.